Breaker elements (also known as stripper elements) are used in so-called bale breaker machine components of bale openers to loosen fibers or fiber flocks out of pressed fiber bales. To do so, the breaker element is moved over the fiber bales.
The bale opener stands at the beginning of process lines in a spinning preparatory (cleaning) machine for processing fiber material, for example, cotton or synthetic fibers or blends thereof and has a significant influence on the continuity of the sequences within the spinning preparatory machine. In the bale breaker machine, the fiber material supplied in bales is loosened from the bales by breaking up fiber flocks and then is transferred to a pneumatic transport system. The pneumatic transport system brings the fiber flocks through pipelines to the downstream cleaning machines. The breaker element is mounted on a movable breaker tower where it can be adjusted in height. The breaker element comprises one or more breaker rollers with teeth mounted on the surface, a restraining element mounted beneath the breaker roller, and a suction hood. Through the movement of the breaker element along the fiber bale, the teeth grip the fiber bales and tear or pull fibers or fiber flocks out of the fiber bale through the rotation of the breaker roller. The fiber flocks thus pulled out are transferred from the breaker roller through the suction hood connected to a vacuum source and supplied to the transport system.
DE4422574A1 discloses, for example, a process for breaking fiber flocks out of textile fiber bales (for example, cotton) by means of a breaker element that can be lowered onto the fiber bales and then moved back and forth over the bales, loosening the fiber flocks from the surface of the bales, and transferring them to a flock transport system wherein the height of the bale is subdivided into at least three breaker zones. To permit optimal processing of the fiber flocks, namely uniform production output and a uniform flock size, the rate of travel of the wagon with the breaker element is adjusted as a function of the bale height.
EP2322701A1 discloses a bale opener, which can be moved at a constant force or a constant height, depending on process conditions. Control is automatic as a function of conditions of the breaker element and of the type of process. U.S. Pat. No. 7,506,410 discloses a bale opener having a movable distance sensor.
The loading force of the contact element of the bale opening must now be measured continuously. However, tests and measurements have shown that the determination of the loading force of the breaker element on the bales is subject to a great many interfering influences such as, for example, the fact that the raising and lowering movements alter the signal, depending on the level at which the breaker element is located at the moment, friction on the rollers that may cause wear, vibrations due to the breaking operation, measurement precision (filters used), etc. Some of these interfering influences are additive, possibly resulting in a measurement inaccuracy of up to ±20 kg or even more in some cases. For example, if a bale group is to be scanned with a 20 kg loading force, this would in some cases result in the breaker element being “in the air” instead of gripping the bales because the controller would assume, due to false measured values, that the breaker element is resting on the bale at 20 kg.
Therefore, before the actual scanning operation is started, the breaker element is lowered slowly until reaching the set loading force, for example, the average of an upper loading force (i.e., raising the breaker element) and a lower loading force (i.e., lowering the breaker element) and it was thus assumed that the breaker element is resting on the bale group at the set loading force. Then the longitudinal drive was turned on and the breaker element was moved up or down accordingly in proportion to the loading force, so that the loading force would come to lie between the minimum and the maximum loading force settings. However, this would lead to the problems described above.